This invention relates to a cooling tower incorporating a cooling chamber with a bottom-to-top cooling air flow, a water injection system consisting of spray nozzles horizontally distributed within the cooling chamber, as well as a first air intake and a second air intake leading into the cooling chamber from below and, respectively, laterally from above the water injection system.
A cooling tower of this type, designed as a wet/dry cooling tower, has been described in DE 29 25 462 C3. Laterally extending into the cooling chamber, constituted of the cooling-tower shell, are cylindrical pipes by way of which a secondary air current is directed into the cooling chamber above the trickling units. The air stream exiting from these pipes is collimated which extends the directional effect of the pipes that serve as flow vectorizers. The radial length over which the pipes proper extend is 20 to 40% of the cooling-tower radius. The wet/dry cooling tower described in DE 29 25 462 C3 is of a radially symmetric design and the cylindrical pipes are evenly distributed over the circular circumference of the cooling tower. This provides for a uniform cross-sectional mixing pattern throughout the flow in the cooling tower. Any other cooling-tower design, especially one deviating from a circular configuration, could be expected to result in a significantly less effective mixing pattern at least in some areas of the cooling chamber while requiring a longer mixing path which in turn would necessitate a greater structural height of the cooling tower.
The invention provides a cooling-tower design with a lateral cooling-air intake, combining a good cross-sectional mixing pattern throughout the coolant flow with the advantages of a low structural height.
As the solution by which this is to be accomplished in a cooling tower of the type first above mentioned, the second air intake is in the form of a two-stage or multi-stage pipe that extends into the cooling chamber and whose stages, starting with the first stage next to the wall of the cooling chamber, feature decremental flow diameters. Preferably, the free outlet end of each stage of the pipe is equal to the flow diameter of that stage minus the flow diameter of the next following stage.
The multistage design of the pipe that extends deep into the interior of the cooling chamber results in a distribution of the cooling air, entering through this pipe, over the cross-sectional area of the cooling chamber. From each of the individual stages only a partial amount out of the total volume of cooling air fed to the pipe concerned will exit so that a distribution of the cooling air is already obtained as it is fed in, resulting in a better overall mixing over the entire cross section of the cooling chamber above the water injection system. Due to the uniformity already obtained at the exit points of the cooling air and the associated improvement in the mixing pattern within a shorter mixing path, the structural height of the cooling tower according to this invention can be reduced, resulting in lower construction costs while at the same time offering advantages in terms of appearance and municipal planning considerations.
If the auxiliary i.e. secondary air flow to be added to the primary air current, constituted of the cooling air fed in via the first air intake, cannot be generated by natural convection, another feature of this invention provides for the possibility of employing a forced-air blower situated in front of the pipe. This forced-air blower is preferably surrounded by a cylindrical blower enclosure, a first partial flow volume of the cooling air exiting from the blower enclosure enters the first stage of the pipe and a second partial flow volume enters directly into the cooling chamber. In this fashion a partial volume of the secondary, auxiliary air current also moves directly into the interior wall area of the cooling tower where it is mixed with the main flow of the primary air passing through the water injection system.
A further enhancement of the cooling-tower design is characterized by an air heat exchanger situated in front of the second air intake. This air heat exchanger is provided with heat-exchanging surfaces for an indirect heat exchange function.
In another proposed design enhancement, the stages of the pipe are axially adjustable relative to one another. This offers the possibility for the secondary air exiting between the individual pipe stages to be directed into the cross-sectional areas of the cooling tower in controlled fashion, permitting appropriate control of the mix ratio.